Process for purifying organic explosive compounds



Patented Dec. 17, 1935 UNITED STATES PATENT OFFICE V PROCESS FOR PURIFYING ORGANIC V EXPLOSIVE COMPOUNDS- No Drawing. Application April 29, 1932, Serial No. 608,345

9 Claims.

My invention relates to a process for the purification of solid organic explosive compounds.

Tetryl, pentaerythrite tetranitrate, and other organic explosive compounds are obtained by nitration processes and the finished product contains impurities in considerable amount even after thorough surface washing of the crystals. The presence of the impurities in the product is shown by the fact that the melting point is considerably lower than that of the absolutely pure product. Recrystallization from a suitable solvent is necessary in order to obtain a product free from impurities.

Various organic solvents have been used for purifying these and other organic explosive compounds by recrystallization, among which may be mentioned benzene, toluene, xylene, carbonl tetrachloride, etc. All these solvents are insoluble in water, and many of them are hazardous because of the inflammable vapors given off which form highly explosive mixtures with air.

Because of the properties mentioned, there is considerable disadvantage in using any of the above solvents for the purpose of purifying organic explosive compounds by recrystallization. For example, the use or" a solvent which is not miscible with water means that considerable dii'ficulty will be met in removing the last traces of the solvent from the crystals. 'In the case of solvents miscible'with water, this disadvantage is not present, since the mother liquor can be readily removed by washing with water. The above solvents are undesirable also because of their high volatility which means a loss of solvent unless unusual precautions are taken. In the case of those solvents which are highly inflammable and whose vapors form explosive mixtures with air, it means also considerable hazard because of the fire and explosion risk. This is particularly so, since the material is dissolved in hot solution with consequent increased vapor pressure.

The object of my invention-is to provide an improved process for producing tetryl, pentaerythrite tetranitrate or other organic explosive compounds in which a product of high purity is obtained by recrystallization from a suitable solvent which is miscible with water and which can therefore be readily removed from the purified product. A further object is to provide a process using a solvent giving rise to no considerable amounts of inflammable vapors to form explosive mixtures with air. Other objects will be apparent as the invention is subsequently described.

I. have discovered an improved process of purifying organic explosive compounds by recrystallization of the material from an organic, non-acidic solvent having the desirable properties of miscibility with water and low vapor 5 pressure, so that inflammable mixtures with air are not formed at ordinary temperatures. For this reason, I prefer to use solvents having boiling points not lower than 100 C.

Various types of non-acidic, organic solvents, 10 particularly of the aliphatic series, are satisfactory for the purpose desired. The higher alcohols of the aliphatic series may be mentioned as one such class, of which amyl alcohol, ethylene glycol and glycerol may be cited as examples. Another suitable class of solvents. is that of the compounds containing the ketonic linkage, by which term I mean to designate all those compounds in which the carbonyl group is present, (00), with the oxygen linked to the carbon by a double bond, the carbonyl group being united either to two hydrocarbon radicals, as in the case of ketones, or to one hydrocarbon radical and one hydrogen atom, as in the aldehydes.

As examples of such compounds, I would cite simple washing with water. Ethylene glycol also is a liquid of relatively high boiling point (197 C.) so that the vapor pressure is relatively low at ordinary temperatures, and there 40 is little loss of solvent. In addition, ethylene glycol vapors do not form explosive mixtures with air at any temperatures that may be encountered.

The solubility of tetryl, for example, in ethyl- V ene glycolis such as to make the latter a desirable solvent for use. Moreover, tetryl is considerably more soluble in hot glycol than in the cold, thus making crystallization of the dissolved material more easy. However, I do not limit the process to crystallization, due merely to the cooling of the solution, since I can obtain similar results by precipitating the dissolved tetryl with the addition of water. This also applies to the otherorganic explosive compounds. 7

By way of illustration, the following specific example is given to illustrate my invention.

Twenty pounds of the tetryl to be purified is brought into solution in 1.5 gallons of ethylene glycol at about 110 C. The solution is filtered while hot and the filtrate is allowed to cool to about C., with or without agitation, which causes the tetryl to crystallize out, or the tetryl may be precipitated by the addition of water to the hot solution. After the greater part of the ethylene glycol has been separated from the tetryl, the final traces of solvent are removed by washing with hot Water. A product of high purity is obtained by this process having a high melting point.

While I have illustrated my invention with particular reference to tetryl; it is to be understood that it applies also to processes for purify-' ing other organic explosive compounds. As examples of such compounds are given trinitrobenzene, trinitrotoluene, trinitronaphthalene, tetranitroaniline, pentaerythrite tetranitrate, and other organic explosive compounds.

I claim:

1. The process of purifying normally solid organic explosive compounds which comprises crystallizing the compound from a neutral organic solvent miscible with water, non-reactive with the compound and substantially free from inflammable vapors at ordinary temperatures.

2. The process of purifying normally solid organic explosive compounds which comprises crystallizing the compound from a neutral organic solvent miscible with water, non-reactive with the compound and having a boiling point above 100 C.

3. The process of purifying normally solid organic explosive compounds which comprises crystallizing the compound from a. neutral organic solvent having a boiling point above 100 C., miscible with water, non-reactive with the compound and the vapors of which are relatively non-inflammable.

4. The process of purifying normally solid organic explosive compounds taken from a group consisting of tetryl, trinitrobenzene, trinitrotoluene, trinitronaphthalene, .tetranitroaniline, and pentaerythrite tetranitrate, which comprises crystallizing the compound from a neutral or- 5 ganic solvent having a boiling point above 100 C., miscible with water, non-reactive with the compound and the vapors of which are relatively non-inflammable.

5. The process of purifying normally solid or- 10 ganic explosive compounds which comprises crystallizing the compound from an organic solvent having a ketonic linkage, said solvent being miscible'with water, non-reactive with the compound and having a boiling point, above 100 C. 5

6. The process of purifying normally solid organic explosive compounds which comprises crystallizing the compound from a higher alcohol of the aliphatic series which is miscible with water, non-reactive with the compound and has 20 a boiling point above 100 C.

'7. The process of purifying normally solid organic explosive compounds which comprises crystallizing the compound from a polyhydric alcohol miscible with water and having a boiling point above 100 C.

8. The process of purifying normally solid organic explosive compounds which comprises dissolving the compound in a neutral organic solvent miscible with water, non-reactive with the compound and having a boiling point above 100 C., removing the insoluble impurities by filtration, crystallizing out the organic explosive compound, separating it from the solvent and washingv the compound with water to remove the last traces of solvent.

9. The process of purifying tetryl which comprises dissolving the tetryl in hot ethylene glycol, removing the insoluble impurities by filtration, crystallizing out the tetryl, separating it from the solvent, and washing the product with water to remove the last traces of the ethylene glycol.

WILLIAM A. SMITH. 

